Stimulatory (Gs) and inhibitory (G(i)) guanine nucleotide binding
protein alpha subunit levels were measured in mononuclear leukocytes from
22 drug-free depressed patients (eight with bipolar disorder, 14 with major
depressive disorder) and a comparison group of 17 age- and sex-matched
healthy subjects. The levels of Gs alpha and G(i) alpha were significantly
higher (160% and 114%, respectively) in the bipolar patients, but not the
patients with major depressive disorder, than in the healthy subjects.
These data add to the evidence for abnormalities in G protein levels and
function in the pathophysiology of bipolar disorder.